Install this version:
emerge -a =app-misc/intellimouse-ctl-9999
If this version is masked, you can unmask it using the autounmask tool or standard emerge options:
autounmask =app-misc/intellimouse-ctl-9999
Or alternatively:
emerge --autounmask-write -a =app-misc/intellimouse-ctl-9999
# Copyright 1999-2020 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2
EAPI=8
PYTHON_COMPAT=(python3_{8..14})
DISTUTILS_USE_PEP517=setuptools
inherit git-r3 distutils-r1
DESCRIPTION="CLI for Microsoft IntelliMouse"
HOMEPAGE="https://github.com/K-Visscher/intellimouse-ctl/"
EGIT_REPO_URI="https://gitlab.com/madsl/intellimouse-ctl/"
LICENSE="GPL-3"
RESTRICT="test"
KEYWORDS="~x86 ~amd64"
SLOT="0"
IUSE=""
RDEPEND=">=dev-python/hidapi-0.9.0[${PYTHON_USEDEP}]"
DEPEND="${RDEPEND}"
>=dev-python/hidapi-0.9.0[]
>=dev-python/hidapi-0.9.0[]