The dotted circle (U+25CC) is frequently used by convention as a placeholder character for displaying combining diacritics without a host letter, that is to say one character cell wide.

Example of the current behavior under default Iosevka:

Example of the desired behavior under Iosevka Term:

Optionally, this could also be extended to Dotted Square (U+2B1A) but its usage for this purpose is less common; however, it would be consistent.