Dave Liney wrote:

The Central Line 1992 stock did have close buttons, and probably still
does. Though I'm not sure they did anything having only used the Central
Line in the central, tunnelled, section where they didn't need to be used.

I remember posters in about the mid 1990s trumpetting this feature, claiming
that it gave passengers the chance to shut out rainy weather at surface
stops. They seem to have since abandoned caring about this.