I suggest making a table of Managers where the Key field is the email address and another field for their name. Then make a relationship where One Manager has many "Form records".
You can populate the Managers table with a few good choices and allow, through permissions, your users to add Managers or flag Managers as being inactive in the Managers table. The advantages of having a table versus a down and dirty multiple-choice field is that if mistakes get entered into a multiple choice field or a manager is no longer valid to be chosen there's no way for these regular empowered users to correct that error. Whereas if you have trusted users they can keep that table tidy and relevant at all times.
Because you don't ever want to really delete manager records I suggest having a checkbox to indicate whether the manager record is active. Then on the form where the manager is being selected through the relationship you were used to report for this filter to include active managers only.
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Mark Shnier (Your Quickbase Coach)
mark.shnier@gmail.com
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