Good advice, thanks.
I actually found a work-around in the meantime that works for my situation.
I was using a filter to find everything that was modified in the last day and upload it to an FTP server. I just want the preview to double-check everything that is being sent, and have no need for 2-way sync or anything. I've made two buttons with the following code:
Go {sourcepath} NEWTAB
Find NAME "Laravel FTP" IN {sourcepath} FILTER
go tabselect -1
Select ALL
Copy FILTER "Laravel FTP"
Go TABCLOSEALL=right
Select * DESELECT
1st button duplicates the current tab, runs the filter, and displays the results.
Assuming you're happy, clicking the 2nd button then selects the previous tab (which will still the display the unfiltered contents of the folder provided you haven't clicked into any other tabs), copies all the files matching the filter. Then closes the tab with the filtered results, leaving you as you started.
This does the job for me.