Horne - who first joined Gregor Townsend's coaching team ahead of the 2023 Guinness Six Nations - was confirmed as part of the setup ahead of the training squad assembling for the first time this week, with 17 Warriors set to report for duty as camp gets underway.
Having won 45 caps for Scotland as a player, the former Howe of Fife man will focus primarily on the contact area and skills, the two areas on which he has focused as part of Franco Smith's coaching team at Scotstoun this season.
The former Howe of Fife man will also dove-tail with Brad Mooar in overseeing Scotland's attack, having worked closely together during this year's Guinness Six Nations.
Scotland play their first warm-up Test in The Famous Grouse Nations Series when they host Italy at BT Murrayfield this July, with kick-off scheduled for 3.15pm on Saturday 29 July.