Overalgebras
In the Overalgebras GitHub repo resides the article Expansions of finite algebras and their congruence lattices, Algebra Universalis, 69, 2013. Also included is the GAP software I wrote for constructing new finite algebras by extending and expanding transitive G-sets, as described in the paper.
An older post
This post is from an earlier period of work and has not been revised since it was written. It is here because it still stands, not because it is current: names, links and affiliations are as they were at the time.
The published version of the paper is in the file DeMeo-Expansions-AU-2013.pdf, and is also available at springer.com.
In the file gap2uacalc.g is a GAP program that can be used on its own to convert GAP groups and G-sets into UACalc .ua files, which can then be imported into the Universal Algebra Calculator. See universalalgebra.org for more information about gap2uacalc.g.
For questions, comments, or suggestions please submit an issue.
Thanks for your interest in this work!
Since this post
The paper appeared as Expansions of finite algebras and their congruence lattices, Algebra Universalis 69:257–278 (2013), doi:10.1007/s00012-013-0226-3. Some links below predate that and point at drafts.