There have been several requests for people to find a way to clear a value in multiple rows. I was thinking about that and came up with a quick example of a way to handle that. Instead of trying to clear a value in an entire column, I realized we could just change one value on a parent column, load it as a single value in our sheet and then compare that parent value to a column that we set or unset for each row. It’s not about clearing an entire column, it’s about making a value in each row not equal to a value in a single parent row. Then you can use an IF/Then column to determine if the ID in the single value column equals the ID set in a column for each row. Using a relation you can bring all selected values back to the parent. Easier to show than explain, so here is a simple example.
This probably won’t work in certain cases, like Add/Edit/Form mode, but if you build it on a detail screen it works great.
BONUS: If you create a Math column, fill it with today’s date, and format it to show date only, then you could create a template column that takes that math column and “locks in” the date formatting. That template column could replace the ParentID column and instead of saving an ID into each task row, you would save the date into each task. This way you could have tasks that would automatically reset at midnight.
Edit: Here is a more advanced version that allows for an option to Select/Deselect All tasks at once. This version feels overly complicated for what it is, but it works. I also added an option to add new tasks, and if ‘Select All’ is selected, the new task will be added as unselected and the ‘Select All’ checkbox will become unchecked. I did discover a bug when adding a new task, where it appears to activate the action on the list item and it was setting the ParentID on the new task, even though my Add Row action wasn’t setting that column value at all. I can only assume that the list action gets triggered. To get around it, I added a Set Column action to clear the ParentID column after the row is added. Feel free to play with it. All Tasks are shared among all users, but task selections are unique to each user.
Edit 2: @Roldy took this a step further and added the ability to save your selections as a preset and later reload any of those saved presets. Here is the link to his post and sample app.