You can tell Trunk Notes to use a different font for editing your wiki pages. Both the font to use and the font size can be set.
To change the font you need to know the name of the font you want to use. A web page which contains a list of available font is iosfonts.com.
Once you have picked a font go to the page Special:AdvancedSettings. You will probably find that this page is empty. Edit the page and set the Trunk Notes variables editor-font-name and editor-font-size. A Trunk Notes variable is set in the format <variable name>=<value>.
That will tell the editor to use the font Menlo-Regular at size 22px (fairly large).
Please note that this file is case sensitive - so Editor-font-name won't work, whereas editor-font-name will.
Once the page has been saved then the new editor font will take affect. Please note that this setting will be synced across devices if using Dropbox sync.