Chord Sheet Maker Online is intended for "chord only" sheets, so rhythmic notation is not supported.
If you need detailed rhythmic notation (e.g. guitar strumming patterns), consider using a different tool.
However, there are some symbols that you can add to your chart to give at least some instructions.
To use a diamond symbol, simply write diamond or <> right after the chord.
See the Example Diamond.
To use a fermata symbol, simply write fermata after the chord.
See the Example Fermata.
You can push a chord by an eighth or sixteenth note by adding < or << right before the chord.
See the Example Push.
To use rests, just write r1 to add a full bar rest or r2 to add a half bar rest instead of a regular chord.
To add a quarter note rest write r4.
See the Example Rests.
To add stroke symbols just write one or more commas , right after the chord symbol.
See the Example Stroke Symbols.