Open App in Photoshop

If you have application in taskbar then use Windos logo + number to run or maximize/minimize application window.

I agree with @Rob_Cullen – Lr to Ps is the order to go...

That being said, it is possible to open a program from Photoshop, but probably not run a menu item.

The following script will run Irfan View, you would swap the path to the program to Lr:

#target photoshop

runIrfanView();

function runIrfanView() {
    var os = $.os.toLowerCase().indexOf('mac') >= 0 ? "mac" : "windows";
    if (os === 'mac') {
        alert("This script is only intended for Windows OS!");
    } else {
        try {
            var progPath = "C:\\Program Files\\IrfanView\\i_view64.exe";
            var progPathOpen = File(progPath);
            progPathOpen.execute();
        } catch (e) {
            alert("Error!" + "\r" + e + ' ' + e.line);
        }
    }
}

https://prepression.blogspot.com/2017/11/downloading-and-installing-adobe-scripts.html

Open Lightroom FIRST, select the files, then use the "Open as Layers in Photoshop..." to open Photoshop.

There is no shortcut to 'go the other way' and open LrC from a Ps keyboard shortcut.. Or pin a LrC shortcut icon on the task bar- takes just one mouse click!

Going LrC > Ps, and then using [SAVE] will automatically send a file back to the LrC Catalog and preserve layers in a TIF or PSD. (Using [Save As] or other methods other than [SAVE]  does NOT return an image to LrC/)

in the future, to find the best place to post your message, use the list here, https://community.adobe.com/

p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post if it helps you get responses.

<moved from using the community>