WYSIWYG Web Builder
This plug-in looks like a step sequencer, but is a MIDI item editor.
It allows you to edit notes on different tracks within one measure bounds
inside a beat grid, by toggling grid cells.  You can move from one measure to another.
Single-mode and multi-mode:
edit either one single track or a number of tracks
Concepts








Insert new items or stretch existing ones automatically
Plugin works in two modes.
In “single-mode”, there are 128 rows for each note pitch of one single track. 
In “multi-mode”, you can add a number of  rows (“channels”) to the grid,
where each one row represents notes of the same one pitch and track of your choice.
You can add/delete notes by toggling cells in rows. If there's no item on channel's track
within  current measure bounds, then either a new item will be automatically added, or
the previous item will be expanded to the end of the measure, depending on insert/stretch
mode option.
Grid time resolution change
You can change time resolution of the grid from 1 beat up to 1/16 beat
(for 4/4 time signature, the range is  ¼ note (4 cells) - 1/64 note (64 cells)).
When you switch to another measure, grid resolution is auto-expanded if necessary
to show all the notes inside the measure.
Copy and paste
You can select one or several rows and copy/paste cell notes between rows in  any mode.
Loop measure
Loop measure option  sets loop points to the current measure and moves edit cursor.