So there were a number of different plans involving the annexation of German territory which went into affect to various degrees.

Firstly land previously annexed directly into Germany during the war time years and in the interwar years were reversed. The big ones were Poland got back a lot of her land, as did Czechoslovakia, Austria regained independence and France got Alsace-Lorraine back for the second time.

The other biggest change was with Poland. The Soviet union kind of shuffled Poland a little west. It too parts of what had been the far east of Poland prior to the 1939 partition with Poland's border being redrawn along the Curzon Line. To compensate for this Poland was given territory that prior to 1939 had been part of Germany with Poland's other border moving west to the Oder–Neisse line based on historic claims dating back to older version of Polish territorial claims prior to its original partition. It also gained territory in its north with the southern half of what had been eastern Prussia. The Northern half of Eastern Prussia was directly annexed by the Soviet Union to become Kaliningrad Oblast due to its value as a Baltic port for the Soviet Navy.

This was in general at least in part to give some extra padding to the Soviet strategic depth along their western frontier.

There were some calls from France to make some alterations to some territory in the Ruhr and Saarland, these being major industrial centres their economic output under French control was useful for rebuilding efforts after the Nazis had looted so much of occupied Europe more or less. Early in the post war era the future of Germany wasn't clear, the possibility of a round four for France Vs Germany was a worry for many. So in that context depriving Germany of these high concentrations of industrial power would have been useful strategically.

. The Ruhr valley plans got smacked down by the other allies pretty quickly but the latter in particular was briefly a separately administrated little protectorate of France and not the nominal occupied Germany in administrative terms. France was hoping to further cement this by turning it into its own country separate from west germany that would be a protectorate of France but they lacked much in the way of public support to continue long term so it got dropped in the 50s.

Much the same can be said of the low country's dabbling with the possibilities of some small concessions. Belgium for about a decade claimed a few scraps of land along its border, though it was pretty minor and likewise as Europe began to look down the path greater unity to achieve peace rather than power politics against each other it gave back its claims in the 50s. The Netherlands angled for some fairly large concessions along its border as reparations but like the French efforts in the Ruhr the allies refused to let it go through.

Germany was already chock full of refugees and some of the western allies feared the annexing German land in the west could lead to a repeat of the interwar resentment Germany had felt. Destabilising it which could lead to either a resurgence as the nationalistic aggressive Germany it has been in the past or potentially fuelling communists.