FR: Enter tags by keyboard only

Since I am quite keyboard centric, perhaps the following would be possible...

### Current situation:
To enter/select tags I can use the dropdown menu to select a tag or use the search field with cursor down and return, where return leaves the input field.

### Possible change:
#### TAB key
If I enter text into the search field, I would like to use the tab key to have
1. partial completion of the most common part
2. full completion if there is only one search result left, leaving the cursor in the input field to be able to select additional tags

Alternatively, let the enter key stay in the input field to add additional tags, and the selection is done by cursor down and enter as it is now, breaking the current behaviour.
#### Comma key
If a comma is entered, I would like to get the current input a new tag name, saving the roundtrip of selecting the + key and creating a new tag. Of the newly created tag is removed from the input, the tag shall not be persisted in the list of created tags.