I am looking for a way to hide a button if a particular item (doesn't) exist. Something similar to @hidepath. For example:
@hideifexists:C:\SomeFolder
@hideifexists:!C:\SomeFolder\SomeFile.txt
I don't think we have that, only checks vs the current path, or vs what is currently selected, when hiding buttons. You can use @ifexists to change what the button does once it runs, though.
Checking if a path exists to decide if the button should be shown or not may not be a great idea as it would mean Opus was constantly having to check that path (and hit the filesystem, or potentially be delayed if it's something like a network drive that isn't accessible) every time the toolbars are updated (which is every time the selection changes, for example). It would also have to monitor the parent folder if you wanted the button to appear/hide when the path it depended on changed. Not impossible, but I'm not sure the trade-offs would make sense.