My attempt for automation all process. Libre 7.6.4.1 Win10
Sub EditText
	dim oDoc as object, oShape as object, oCur as object
	oDoc=ThisComponent
	for each oShape in oDoc.DrawPage 'get the shape by the name
		if oShape.Name="myShape" then
			rem select text in text box via textCursor
			oCur=oShape.createTextCursor
			oDoc.CurrentController.Select(oCur)
			wait 10
			uno(oDoc, "SelectAll")
			wait 10
			uno(oDoc, "Copy")
			wait 10
			exit for
		end if
	next
	rem remove Text Box
	with oShape
		.ChainName=""
		.TextBox=False
		.TextBoxContent=Nothing
	end with
	rem Paste to Shape
	oDoc.CurrentController.Select(oShape)
	keyPress(oDoc) 'F2
	wait 500 'sometimes lesser value doesn't want to Paste copied text
	uno(oDoc, "Paste")
End Sub
Sub uno(oDoc as object, s$, optional arr())
	on local error goto bug
	if isMissing(arr) then arr=array()
	s=".uno:" & s
	createUnoService("com.sun.star.frame.DispatchHelper").executeDispatch(oDoc.CurrentController.Frame, s, "", 0, arr)
	exit sub
bug:
	bug(Erl, Err, Error, "uno")
End Sub
rem key pressing
Sub keyPress(oDoc as object) 'simulate F2/Enter press in oDoc
	rem !!! this can cause the triggering of window elements.
	dim oKeyEvent as new com.sun.star.awt.KeyEvent
	oKeyEvent.Modifiers=0
	oKeyEvent.KeyCode=com.sun.star.awt.Key.F2 'or .RETURN
	'oKeyEvent.KeyChar=chr(13) 'can use for .RETURN
	simulate_KeyPress(oKeyEvent, oDoc)
End Sub
Sub simulate_KeyPress(oKeyEvent as com.sun.star.awt.KeyEvent, oDoc as object)
	if NOT isNull(oKeyEvent) then
		dim oWindow as object, oToolkit as object
		oWindow=oDoc.CurrentController.Frame.ContainerWindow
		oKeyEvent.Source=oWindow
		oToolkit=oWindow.Toolkit
		with oToolkit
			.keyPress(oKeyEvent)
			.keyRelease(oKeyEvent)
		end with
	end if
End Sub