In PsychoPy 2021.2.3 (using Javascript):
The dollar sign ($) as code indicator in any TextBox’s Text property appears to be foiled by another dollar sign.
So this works: $Math.E+'%' generates 2.72% as expected.
But this does not: $Math.E+'$' generates Math.E+'$' instead of 2.72$.
This also behaves strangely: $Math.E+'\$' generates 2.72\$ instead of 2.72$.
This functionality used to work in previous versions of PsychoPy (eg, 2020.2.4). The issue may be related to '\$' solution for text with dollar signs no longer works on Builder or Use $ symbol and mulitple colors in the text - #7 by feinbergdavid
A workaround: $Math.E+String.fromCharCode(36) generates: 2.72$ as expected.