I would not underestimate basic enlightenment. I remember my first ancient
disappointment when a textbox in an embedded chart dismissed when moving the
chart. If you try to insert a textbox into an embedded chart which has not
been pre-selected, the textbox stays stuck on the background worksheet, and
you see or not see it dependent on what is just selected. In the opposite
case, the textbox is fixed to chart area (the whole picture/shape) and not
plot area (the rectangle with markers, lines etc.). So if you then place
textbox elsewhere, it keeps the overall position, it is proportionally
changing with changing chart sizes (caution with font size! – delete
Automatic scaling). If you, however, want to have the textbox bound to plot
area, e.i. fixed to markers etc. while you reckon with changing the plot
content or size or position within chart area (it may come in small
automatically if you change the length of axis label numbers), then Jon’s
method is indispensable.