Totalling days/hours estimates for each category
For each task, add an estimate for the days or hours for that task. Then for each vertical, provide a sub-total of the days/hours recorded in each task.
Similar to what Trello does already.
Greg Garcia commented
This is very useful to several organizations I've worked for. It allows a team to gather around planner and see how loaded everyone is on the team. This info feeds into maximizing team output and headcount decisions. Also makes folks ask the question, "Why does that take X Hours?" Can we somehow do that faster? A tool for teams to help hold each other accountable.
As long as adding numbers for estimations to cards, you may want to use this Chrome extension: https://chrome.google.com/webstore/detail/estimations-plugin-for-mi/opojklifmgglalpfgbhfnocboncbfcdj?hl=en-US
If you add estimates in brackets to the card's title, the plugin will highlight this number and sum the numbers of a column. Of course, this is just a work-around, as long as Microsoft doesn't add extra fields for estimates.
Stuart Bruce commented
This is an absolutely essential feature. It would be good, but not essential, if there was also a field to track the actual time spent on the task. Even better if the API could link this field to Toggl to make it easier to record the time. Although if the API was on Zapier or Flow then this could be done.