JabRef version 5.2, 5.3 and 100.0.0 (commit 0dd4de7) on Linuxmint-20.1 and LinuxMint-19.3.

• [x ] Mandatory: I have tested the latest development version from http://builds.jabref.org/master/ and the problem persists

File rename commands are greyed out and not active, and the reason is not clear for the user. Moreover, these commands are inactivated at the moments when they are badly needed!

Steps to reproduce the behavior:

1. Start the relevant version of the JabRef;
2. Load some .bib library; the file used for testing is in the .zip below:
   new.zip
3. Populate directory "new/" with some OA PDFs having the same names as in the .bib file;
4. For testing, the following settings were used:
   -- Autolink files: use regular expression **/[year]_[auth].*\\.[extension];
   -- File format pattern: [year]_[auth]_[firstpage];
   -- File directory pattern: by-author/[authIni1]/[auth];
5. Right-click on the file linkage box in the entry editing window;
6. For version 5.2, both "Move to file directory..." are always disabled, but "Rename to a defined pattern" is active and works:
   
7. In 5.3 and 100.x (the current master tip), the "Rename to a defined..." and "Move to file directory and rename..." are enabled at the beginning, but are disable after the first rename, with now means to reenable them except shutting down the whole JabRef and starting it again. Changing the BibTeX entry (e.g. adding page numbers, that potentially change the "defined name pattern") does not re-enable these fields:
   

Either the commands should be re-enabled after edit, or not disabled at all; otherwise the renaming feature (which I use a lot!) becomes next to unusable...