Implement an autofill function for the tag field (when creating a card)
When I create a new card I would usually choose the tag first. If I have lots of tags (more than 5), and even more if they are long, it's annoying to type the tag every time. Or to scroll up and down to the right tag. Or to click the dropdown menu with the mouse. Would be really nice to have an auto-fill option where when I type “C” it suggests the last/most used tag beginning with “C”, e.g. “Computer Science”, and I just have to press Enter/Tab to jump to the input field.

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Alex Wenman commented
Feedback on your idea and example: It might be implied in your suggestion, but I think that the autocomplete should allowed multiple character entries. Using the example above, typing "C" might suggest "Computer Science", but it might also suggest "Commerce", and "Chemistry" depending on last used. Typing "Co" will only list "Computer Science" and Commerce". Finally, typing "Comp" will only suggest "Computer Science".
Sorry if this feedback is a bit pedantic.