Running a script within an action

Mockup image creation is a very simple thing to automate using the Batch Replace Smart Objects plugin for Photoshop. Basically, just select the Photoshop document to use (in this case, your mockup images of the jar which contains the Smart Object), the input folder of your images (in this case, your label designs), then the output folder to save the final images to.

However in your specific case, note that I don't think this plugin will work for complex .psd documents that have multiple Smart Objects that all need to be replaced. Like, if you have a Photoshop document with 2 or 3 jars, and you want all 3 of the jars updated simultaneously with the one artwork images or label design? I don't think this plugin will work. I've only used it for mockup images with one single Smart Object that needs to be replaced with images (such as apparel mockups featuring one hoodie, or wall art mockups featuring one art piece.)

If you're doing something super complex and customized like that, really I don't think there is ANY kind of pre-built template script or software that can do that for you. Something that highly customized will almost certainly require a separate, standalone .jsx script that's specifically built for the exact workflow and set of Photoshop documents you're using. There was another guy on these forums who posted a similar question inquiring about how to batch-generate mockups when the .psd documents contain 4 separate wall art mockups -- each needing to use 4 different artworks designs, grouped together in sequence but iterated through as groups of 4. Like if you're doing THAT level of complexity, the only answer is a custom script designed for that exact unique workflow.

If possible for what you're doing, it'd be way easier to simplify your workflow + stick to just one mockup at a time. That way, you could just use a Photoshop plugin or simpler .jsx script to automate it by iterating through all images in your input folder. Is it absolutely mission critical that you create product images featuring 3 jars instead of 1? Do you have any valid reason to believe that your conversion rate will substantially drop if the product photos feature just 1 jar instead of 3 side-by-side like that? Not trying to be a smartass, but honestly, you might be very needlessly overcomplicating things just to try to create a much more complex image when a much simpler image will be exactly as effective at driving conversions, satisfying the client, or doing whatever it is that you're trying to do. I would honestly ask yourself: "Would a simpler mockup automation workflow be exactly as effective for achieving my ultimate goals here? If so, why am I making things so much more complicated than they need to be?"

This more complex stuff -- I mean if you don't know how to write the .jsx scripts yourself, you'll probably have to hire a freelancer who specializes in Photoshop automation to do it for you. (You can find some on Upwork if needed -- just search Photoshop automation or Photoshop scripting or something like that.)

Photoshop cc 2019 doing some strange things;  I redid all the templates and labels.  I had left the 41 label layer in the templates smart object. So I remove all but one and changed the one remaining label opacity to zero so it would not be visible in the templates.  I change all the label file format from png to psd for when I have edited png objects the save took a long time.  The smart object is your template was created in photoshop from a raster layer so when it is opened in Photoshop.  Photoshop creates a PSB work file for the object. So PSD in more in line with psb.  CS6 did not fail. CC 2019 fails consistently populating the 04LM mockup when batched with all 84 mockups but not in the same place.  It does not fail if I just populate the 04LM template or all the mockup before 0LM4 and 04LM.   When I saved PSD as well I notice the jpeg files have the wrong date. The PSD files have today's date the jpg yesterdays date.  In the 04LM Output PSD files, the last PSD with two alike labels is messed up though it looks correct it must have been where the replace content was canceled by the user. All the  04LM PSD file after the only have the small label updated.  If I try to update the last PSD with two identical labels the update of the object fails with a program error. If I try a second time there is no program error, however only the small jar label layer updates.  CC 2019 has some issues and the kind the will be very hard for Adobe to track down and fix.   

CC 2018 seems to hang if I leave the machine alone. When I come back and play with the mouse CC 2018 seem t0 get out of its funk and continues to populate templates.

I testing CC 2019 at this moment batching all 84 templates it has passed the 04LM template this time without the user canceled operation error I think it is going to be very hard for Adobe to track down.

Today I added a timer to the script to time how long it runs.  I also recorder an Action to create Candy Jar Mockup from your layer group  player it 84 time to create your mockup templates and ran the script.  I walked way and came back some time later.  The script was displaying a Photoshop error it  had caught which pauses the script.   The message was user canceled. Since the script was into processing the mockup templates  at that stage all the the script does is replace Content and save as jpeg.  It was processing the 04LM Mockup template so I let the script continue  and look at the output.  It looks like it is a bug in Photoshop the Replace Content messed up and did  something very strange to the current document. The first 22 Replace content  worked and all the save jpeg worked al 3,444 mockup were save.  However in the 04LM while the first 22 are correct the last 19 are not.  While there is only one shared smart object label that is on both jars the last 19 mockup have different  labels on the jars  which should not be.  So CC 2019  must have so,e weird bug. The net result was there were 3,425 good output files and 19 bad output files. It too 2.7 hours but I doe not know how long the script was pause displaying the  error message.  Here is a Capture of CC 2019 Problem. I may try CS6.

Sounds like multi-step workflow may be better than trying to do it all in one file.

1) Setup variants in spreadsheet

2) Create variables/data driven graphics in Photoshop, Illustrator or InDesign (data merge).

3) Save out flat labels for each variety and size etc.

4) Batch the placement of the flat labels onto the jar, warping and saving out final files

Can you post screenshot with example. Please include and Layers panel.

Look up data-driven graphics. You would save the labels out at separate files, create a spreadsheet that specifies which label graphic goes with what, and create a master image that has the data set imported. If I had to do this every month, that would be my first idea.