Just to make it clear, this PR is ready for review.

Test project: test_input_virtual.zip

The tests on 2 devices were ok. (Google Pixel smartphone and Samsung tablet)

Can LineEdit from SpinBox also be displayed in the Inspector?

%SpinBox.get_line_edit().virtual_keyboard_enabled
%SpinBox.get_line_edit().virtual_keyboard_type

class SpinBox : public Range {
	GDCLASS(SpinBox, Range);

	LineEdit *line_edit = nullptr;

---------

void SpinBox::set_editable(bool p_enabled) {
	line_edit->set_editable(p_enabled);
	queue_redraw();
}

Test project: test_input_virtual.zip

The tests on 2 devices were ok. (Google Pixel smartphone and Samsung tablet)

---

Can LineEdit from SpinBox also be displayed in the Inspector?

Details

%SpinBox.get_line_edit().virtual_keyboard_enabled
%SpinBox.get_line_edit().virtual_keyboard_type

---

Maybe like editable.

(a clean solution would probably be inheritance, C++ allows multiple inheritance, but only one class can be passed to GDCLASS, I think)

class SpinBox : public Range {
	GDCLASS(SpinBox, Range);

	LineEdit *line_edit = nullptr;

---------

void SpinBox::set_editable(bool p_enabled) {
	line_edit->set_editable(p_enabled);
	queue_redraw();
}

We can do something like editable. I just didn't exposed it to inspector as there is no need to change the keyboard type to anything other than number for SpinBox.

I encountered an issue where, the keyboard type for TextEdit switches to multiline keyboard after submitting/pressing enter, instead of retaining the specified keyboard type. I'm marking this as a draft until I resolve the issue.