Editing off SSD

Is there a way to put the SSD in Lightroom so that Lightroom will recognize the photos all the time?

By @defaultt9aobyx28ayi

The list of the contents of the SSD is preserved in the Lightroom Classic catalog, so there is no problem. It has not forgotten about anything, because if you plug in the external SSD again, the question marks should disappear as Lightroom Classic follows each image’s last recorded folder path to reconnect to the originals. The question marks only tell you that the original media is not connected at the moment.

Because the catalog remembers the original file locations, you can do a lot with the images like organize them, add keywords, etc. even when the external SSD is not connected. But some direct edits such as Develop module options are not available if the original media is disconnected; for that you have to plug in the SSD. Also, when the SSD is disconnected, if an image hasn’t had a preview built it may appear blank until the SSD is reconnected.

You can create Smart Previews for the content of the SSD. Smart Previews stay on your laptop so that you can do almost anything with the photos on the external SSD even when it is disconnected. They are handy, but there are some disadvantages to creating Smart Previews:

• Smart Previews are limited to 2560 px on a side, so if your originals have larger pixel dimensions than that, you won’t have access to all of the original details, which may affect sharpening adjustments and exporting at large dimensions. 
• Smart Previews do take up space where the catalog is, so if you keep the catalog on your laptop and you want Smart Previews because you don’t want to plug in the external SSD all the time, then you still have to account for the space the Smart Previews will use on your laptop. Smart Previews do need less space than the originals, and you don’t have to create Smart Previews for everything on the SSD, only the images you expect to edit. Like if you want, you could create Smart Previews for just the last year of photos you took, or just for the job you’re currently editing. 

I prefer to not have to think about it, so when I want to use Lightroom Classic to edit the originals on my external SSD, I just plug it in, takes 5 seconds.

Smart previews are indeed the answer. The size should not be a big problem. A smart preview is about 1MB, and you can selectively build them and discard them again.

You can create Smart Previews so most functions in Lightroom Classic work even when the SSD drive with the photos is not plugged in. However, Smart Previews take up space on the internal drive, and so only you can decide if they take up too much space or not.