Is it possible to create a special character and add it to special characters?

I have to type up papers with medical abbreviations. 4 common abbreviations are ā, p, c, s (also with a line over them like the ā). Right now I have to use a text box with the line in it and place that over the letters p, c, and s, set the txt box to be in the background but selectable. Then every time I edit the document the line moves separately from the letter and you can imagine what a pain it is. I'd like to create these characters, add them to special characters and then insert from there.

Does anyone know of a way to do this via special characters or know of another way to accomplish the same thing?

Solution 1:

You can add a line over p, c, s either with the US Extended keyboard layout (base letter then option/alt + a) or the Character Viewer (double click on unicode 0304 after the base letter). Best just copy them from here:

p̄ c̄ s̄

You may need to try different fonts to get them to display properly

Solution 2:

You would either need to create a font and add these characters to it, or find a font that contains these characters already (which I would imagine is possible if they are used commonly in a field).

In terms of accessing the characters, since they will probably be way off in the extended character set and not easily typed, look at the System Preferences > Language & Text settings, on the Text tab, and create a substitution. You could set it so that typing the letter "a" followed by a hyphen and a space substitutes the character "ā", for example.

Solution 3:

Look at the answers to this question. Especially useful might be the approach in this answer to edit the values in /System/Library/Input Methods/PressAndHold.app/. You could make it so that holding p would pop up a list of options including p̄.