Secure / encrypted
I wish to suggest adding a feature to encrypt the directory of specific tags that contains personal data and passwords. This would be very useful to Linux community as such tools are rare.
Encryptions goes out of the scope of the project. There is plenty of encryptions software available, which can be used in combination with TagSpaces. (e.g. TrueCrypt).
Max Pittsley commented
I think you would need to do this on a per-file level, if it were a feature of TagSpaces, rather than per-directory since directories and tags don't correlate with each other (unless you make it so by hand, in which case why would you even use TagSpaces?).
If you wanted encryption on a certain directory, rather than a certain tag (as you first stated), I'm sure a third party tool would do the job, like Seahorse.