Typically, Office spreadsheets reside on the local computer, or if confidential, on a drive that's removed and locked in a drawer. Once you start entering things into an on-line service, you're at the mercy of whatever security or motives are involved in that service.
I'm not quite sure where the line is, but for myself, I'd suggest that at the moment you're acting in the capacity of a church leader and entering data about other people into a system not approved by the church, you're entering a "gray zone". Especially when you're dealing with a system that "understands" what the data is (unlike a spreadsheet or a word processor that just deals with words and numbers).
Some of those functions on Clerk Tools are fine, but some of them require entering names of people and some information about them. The question then becomes how much information is too much?
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