In most tagging software I've used you can add multiple tags at once by typing them all in the entry field, separated by commas. In Tropy I have to type one, hit enter, type another, etc.
Is this a possibility for Tropy?
An extension of this idea: making groups of tags that I can apply to files with a single click. I'll use Picasa's tagging system as an example: at the bottom of the tagging portion of the interface were 10 or 12 buttons, each of which could have one or more tags assigned to it. In my case there would be one that applied bird/birding/birds, one that applied my kids' names, one that applied insect/arachnid, and so on. Sometimes I'd have buttons that had 5 or 6 tags. And changing them was easy, so I could create useful buttons for whatever I was working on. Then I could look at a folder of images, select every one (no matter how many) that needed a specific tag or tags, and apply with one click. (Picasa would allow tagging any image format it could display, even ones that aren't taggable, like Photoshop and RAW files. Their tags would only be visible inside the program.)