Hi @Kaito_at_Pear,
You can work around that by making a Dates table where the Primary field is just a set of dates that the user can choose from. I see there are dates and times, but that would be just undoable. Instead of having 7 date fields, you can have only one date field that links to the Dates table and users can choose any number of dates.
After doing so, you can use Rollup field with ArrayUnique in the Events table (which will also be linked to the Dates Table) to get a list of the people available on that date.
If you want to get around the Link to another record part with the user, you can leave the form as it is but create a Zap that copies the dates from the 7 fields and pastes them into a Link to another record field, make sure the Primary field in this table is not a formula so that Zapier can create a new record if it doesn’t already exist.
Hope this helps! If it does, please mark it as a solution so others can see it.
BR,
Mo