I agree with almost everything you wrote, Helmut. In my ancestry.com tree, I have Margarete being born in Saxony as well. I have not edited her profilein Wikitree. Where I disagree may not be a real disagreement. However, as you noted, Johann I (Wettin-104) had a daughter Margarete. Therefore, it would follow that Von-Sachsen-126 should be connected to Wettin-104 and his second wife, Margarete von Anhalt, who should be added to his profile.
The error, as you pointed out without saying so directly, is that Von-Sachsen-126, if she married Hans Buser, Freiherr von Liestal, [Buser-208] may not have been the father of Hans, fils, who was born three years after her recorded death. Thus, more work needs to be done to establish that she was the mother of Buser-206, my direct ancestor.
I, too, had recorded Von-Sachsen as having died three years before Buser-206's birth. I just figured that something was wrong but I did not know which and whose date was wrong.
The Wikipedia.org listing for Buser-208 discusses this issue. The source, however, for the date of death of Von-Sachsen-126 as well as her mother is not an original source but, rather, an 1870 publication. Here is what is found in Wikipedia.org.
For Johann the Steadfast’s child “Margaret”, an unsourced statement is present indicating marriage to one “Hans Buser, Freiherr of Liestal” on 10 June 1536. The previous unsourced date of death for Margaret was stated as 1545 which would allow for a marriage on that date; however, Behr (1870) indicated her year of death as 1535 (p. 141). As such, a marriage date of 1536 is unlikely and dubious. Given the lack of citation for this marriage, and for a date outside of the documented lifespan for Margaret, additional credible/reliable sources are needed to validate whether 1) A marriage between these lines occurred and, if so, then 2) On what date did said marriage actually occur. Noting that Behr (1870) does not list a spouse for Margaret in his book.
References Behr, Kamill von (1870). Genealogie der in Europa regierenden Fürstenhäuser nebst der Reihenfolge sämmtlicher Päpste (in German). Tauchnitz. p. 141. EB62001 (talk) 02:53, 12 February 2019 (UTC)