Steps to reproduce this issue

1. Step 1; create a new table with a BLOB type column;
2. Step 2; add a KEY to it;
3. Step 3; save;

You will receive the error "SQL Error (1170): BLOB/TEXT column 'column1' used in key specification without a key length", which is right, due to BLOB type requires a key length.

For VARCHAR type we can modify the Length at Indexes tab.

But for BLOB types we can't:

I could check that all VARCHAR similar types will works, and all BLOB similar types will not.

Workaround

Currently workaround is modify the Datatype to VARCHAR, modify the Length then back to BLOB.

Possible solution

Seems related to this piece of code. Maybe just do Allowed for dtcBinary, except if exists some reason to it.

Environment

• HeidiSQL version: 10.3.0.5885
• Database system and version: MariaDB 10.3
• Operating system: Windows 10 x64