I'm trying to reverse a bigger structure used in an old game. Obviously I didn't know all fields when I created the structure type, and now I want to edit in some new fields / change pure byte gaps into meaningful fields.

This, for example, is a structure of a GuiButton which I know by now, but it's just a gap yet: enter image description here

I don't find any way to edit the field of the structure. Do I have to completely delete the existing structure and create a new one? enter image description here

2 Answers 2


You can undefine the field (select Undefine from the context menu or press U) and then press D to define a new field in the gap.


Position cursor where you want to insert (cannot be at the structure end) and press Ctrl+E (see expand command in IDA documentation).

  • Is this a new feature, by the way? My question is from 2016, and if I recall correctly, Ctrl+E always appended bytes even if the cursor was in the middle of the struct. But I may have just been blind back then.
    – Ray
    Oct 2, 2021 at 14:01

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