Script for selecting layers / files from the drop-down menu.

In this thread they gave me the correct answer, thank you very much.

https://community.adobe.com/t5/Photoshop/Script-for-selecting-layers-files-from-the-drop-down-menu/m-p/10689092#M272073

I may be wrong, I'm only a beginner... My understanding is that scripts "run" until they have completed running, they will retain focus and not "float" and will not allow the user to do other tasks like a normal Photoshop panel would do.

An extension/CEP/HTML panel can float and allow other areas of the GUI to obtain focus and be used while the panel is visible in the GUI.

If my understanding is correct, then the issue is about the floating (modal?) nature of scriptUI windows taking focus while running and once exited they no longer appear/float like a standard panel, they are a window/dialog object not a panel.

If you want a floating panel, then this is beyond scripting and you will need to develop a full HTML extension panel. There was a forum for this however I don't know if it survived the forum update or not. Here are some links in no particular order:

https://medium.com/adobetech/how-to-create-your-first-adobe-panel-in-6-easy-steps-f8bd4ed5778

https://medium.com/@hallodom/starting-photoshop-html5-extension-development-f19e366373d8

https://github.com/Adobe-CEP/Samples

https://www.htmlpanelsbook.com

https://creativemarket.com/blog/how-we-built-a-photoshop-extension-with-html-css-and-js

https://creative-scripts.com/cep-what-to-know-and-where-to-find-it/

var layerName = prompt('Enter a Layer Name to Select', '');
app.activeDocument.activeLayer = app.activeDocument.layers.getByName(layerName);

The code above is what you would like to have in a graphical "pick list" format? So, a window or floating panel that has a drop-down menu with a list of layer names (instead of entering them into a prompt), one then selects the layer name from the list and presses OK and then the layer is selected in the layers panel?

What do you mean by a drop-down menu? You can use the Layers panel to select layers. As for selecting files from a folder, File->Open command is the most direct.