Pretty_Print / show seems to delete trailing spaces:
reset()
var('x t')
Psi = function('Psi')(x, t)
V = function('V')(x)
show('Plug ', Psi, ', ', diff(Psi, t), ', ', diff(Psi, x, x), ' into ', V)
See after "Plug" and after "into" (screenshot taken from CoCalc Jupyter Sage 8.9 Kernel):
