Hi @akashkekan ,

you have to save the record in order to make the UI Action to be visible for the mentioned category

if you want this to visible or hidden onChange of the category use onChange client script on the task category field 

refer this for the same

https://www.servicenow.com/community/itsm-articles/how-to-hide-show-the-ui-action-by-client-script/t...

Note: this won't work in the workspace

Please mark my answer as helpful/correct if it resolves your query.

Regards,
Chaitanya