This is similar to the setting in astro,com (which is used with sec prog. in RA):

Progress MC by SA in Long

Please note that selecting Naibod by Longitude, or Mean Quotidian disables the switch button. Progressing the MC by Solar Arc in long applies only to Naibod by RA.

Example Chart with MC progress by Solar Arc

Note the text at the top of the chart /MC SA which = MC progressed by Solar Arc

Example Chart with MC SA

Example Speculum Listing – Aspects tab button tapped.

Showing MC SA in the title heading

Speculum MC SA

Helpful summary when using Aspect Hits

Summary of Progressions and Directions settings