[Edgemeal]

Using the js_ReaScriptAPI extension you could try something like this,

local title = reaper.JS_Localize('Resources', 'common')
local hwnd = reaper.JS_Window_FindTop(title, true) 
local filter = reaper.JS_Window_FindChildByID(hwnd, 0x466)
if filter then
  local track = reaper.GetSelectedTrack(0, 0) -- get first selected track
  if not track then
    reaper.JS_Window_SetTitle(filter, "")  -- erase text in filter
  else -- set filter to name of first selected track
    local _, track_name = reaper.GetSetMediaTrackInfo_String(track, "P_NAME", "", false) 
    reaper.JS_Window_SetTitle(filter, track_name)
  end
end