how do i manually add text to a cell that has an IFS function?

If the cell already contains a formula, it cannot also contain user-input text. Nothing prevents you, though, to clear the formula in cell A1 and replace it with your own entry if B1 is set to “interpolated”. Alternatively, you could add a new column (let’s say Column C) where you would enter comments specific to the type “Interpolated” and modify the A1 formula to refer to cell C1 when B1 is set to “Interpolated”.

I'm not quite sure I understand what's happening - other than if you're just trying to add text to the end of the function, that's doomed to fail unless it follows the format that the formula expects...

In this case, IFS() requires pairs of parameters. For each pair, the first item consists of a boolean (true/false) condition, and the second is the value to return if that condition returns TRUE.

You can have as many condition/result pairs as you like.. the first one that returns TRUE will indicate the value that is returned. If none of the conditions return TRUE then IFS() will return an error (for this reason, IFS() often has a 'catch-all' condition at the end to act as a default value).

In addition, when writing this function in particular, you may find it easier to break each condition/result pair into a new line - this makes it much easier to read and follow the flow. Use option-return in the formula editor to enter a newline.

So, that said, here's an example:

You can see I've added a catch-all TRUE() at the end so that if the source cell contains any other value it returns the string "Error" - this may not be necessary if the source cell can only contain items from the pop-up menu, but it's a worthy check.

In either case, to add more conditions, just insert a condition/result pair in the same format (leaving the catch-all as the last). e.g.:

As long as you maintain combinations of condition/result pairs, you should be fine.

That said, for this kind of calculation, there may be an easier solution, especially if the list changes frequently.

If you create a second table of two columns - the matching pop-up menu items and corresponding values, you can perform a simple lookup. For example, I created this simple table:

(this can be on a separate sheet if you want to get it out of the way). Now the formula on your main sheet can just say:

The LOOKUP() function will look for the value in Condition Kwspacing in the Condition column, and return the corresponding value from the Result column.

Now changing the list of options, or the required spacing/return values is as easy as adding a row to the table, and all the cell references will honor it (as opposed to having to extend the IFS() formula across all the cells to update to the new values).

(Site note: it would be nice if the pop-up menu could reference this table, too, so that they're always in sync, but Numbers doesn't support that, so you're still on the hook for editing the pop-up menu to have all the options)