Add an Omnibox: to search and add todos, projects, labels, dates
Adding a todo in todoist feels a bit clunky. You could cut down on one click, if you implement an omnibar at the top.
This omnibar could simply always be at the top, not adding too much clutter. If I click into it and start typing I get instant search result suggestions for matching todos, deadlines, lables... you name it (like instant search on Google). And below that, or if no search results are found, I get the add a task menu.
Now I can either click on a found item, e.g. a label or fill in the due date and project and click on "add task".
It saves me a click and it also prevents me from making double entries because I will see existing items because of the instant search capability.
As you already have a search bar in the left column and this would replace its functionality, the original search bar is no longer required, meaning this additional feature is not cluttering up your space more, it is actually removing an element (the round plus button) making Todoist more minimalistic.