defining the PERMISSIVE_HOLD and IGNORE_MOD_TAP_INTERRUPT config.h options enables applying responsive modifiers to the home row, for vastly improved accessibility.
The redundant center column modifier chords are now replaced with layer toggles, freeing both hands for those instances when a switched on layer is convenient and allowing additionally defined keys.
the single handed home block symbol cluster has since been refined for additional scope and ease of fingering..
the following layers are the switchable layers in addition to the usual momentary layers, Shift, Numeric, Symbol, Function Key, etc. With both hands free, the Numeric and Regex layers add a few extra useful keys while retaining the mapping of their momentary layer counterpart.
Tapping the layer key a second time or, more conveniently, pressing the Escape key, toggles the layer off and returns to the base layer. Tapping an alternate center column key switches immediately to the layer or function (Caps) without need to toggle off the current layer..
with the left thumb now free, the Space key is now accessible..
an oddity as a switched on layer but easily implemented..
capitalizes on the left and right hand home block symbol clusters, aiding familiarity..
The (redundant) Dollar sign, Underscore and Tab keys are replaced with Question mark and Plus sign regex characters, and Space. The freed hand reach adds the Ampersand, Percent and At sign characters to the regex symbol set.
with the Splitography keyboard quickly becoming my daily driver, aligning the thumb key assignments of the Planck (while appearing somewhat odd) reduces finger memory issues between the keyboards..
(Since updated to the BEAKL 8/EZ+10 layout mashup..)