The dim7 is also named diminished seventh
Use °7 instead of dim7
Use o7 instead of dim7
A dim7 is a Diminished chord
How to construct a dim7 chord?
Use the following intervals in any order to construct this chord. Start on a specific note on which you want to construct this chord from (for instance the note "C") and calculate each interval on top of it. Afterwards, you will be able to play it on your instrument.