I separated this question into a new topic as it would be best to stick to the main topic if possible.
(which in the original thread was more about limbs deformation)
Regarding your question,
[trim:mask] can be used on layers and folders so yes, you can use it on a folder.
Please refer to the user guide for the correct usage:
https://esotericsoftware.com/spine-import-psd#Tags
Please note that this page and this tag only apply to the Import PSD function.
This mask function is not available in the Photoshop ti Spine script. You can find the list of supported tags for that script here:
EsotericSoftware/spine-scriptstree/master/photoshop