Hookpad organizes its chord by function, rather than by chord name. For example, inversions of I and V in C major would be: C/E, C/G, G/B, or G/D.
Bm7/E isn’t really a “simple” slash chord, and to understand how that chord functions takes a bit of music theory.
The notes in that chord are: E, B, F#, D, A
If the A were a G, then the chord would be an Em9 (E B F# D G), but to make the G an A requires us to suspend the 3rd.
So that means that Bm7/E is enharmonically equvalent to Em9sus4
To get this chord into Hookpad we need to first ask which key we’re in. For example, that chord probably doesn’t have a lot of function in C major, but may make more sense in G major or E minor instead, where the F# is diatonic. An Em9 in the key of G is a vi9, so its suspended version would be vi9sus4
You might wonder, what’s the purpose of thinking of this chord as an Em chord rather than an a Bm chord? The reason is because its musical function will act much more similar to an Em chord, and your knowledge of how Em chords work in G Major will help you understand how to use this chord in your songs.
For example, if I’m writing a chord progression that uses this chord, I might do something like:
I7 → vi9sus4 → vi9 → ii9 → V11
Here I’m using the fact that I know that vi chords are good bridges between I and ii and I’m using the dissonance from the 9th to inform the complexity of the other chords.