Simunek stepped down as Europe CEO earlier this year after four years in the role. Scholefield becomes chief executive for the region, with Jukes chairman.
The Huntsworth-owned agency said the move will "help deliver greater integration" across the 17 markets in European where Grayling has a presence.
It will also "encourage further collaboration, not just between offices, but also between practices and services, in line with client needs and expectation".
Huntsworth CEO Paul Taaffe said: "Sarah and Richard have a proven track record in the UK of driving growth and change to meet the ever-evolving needs of clients and I am delighted that they will bring this experience to all of our Grayling European offices."
Scholefield said: "Bringing continental Europe and the UK under one structure and united leadership reinforces our determination to share best practice and insights from across the region to the benefit of our clients and our staff. We already work closely with our European colleagues on a number of clients and in multiple markets and I look forward to continuing that close collaboration and building on our shared culture and aspirations to develop this further."
Jukes said: "We have a very robust portfolio of services across both the UK and Europe, but at a time of significant political change and realignment, clients increasingly want access to a comprehensive public and corporate affairs network, operating on the ground in the markets where they too operate. By further boosting Europe’s strongest public affairs network, we will create a significant opportunity to extend our services further, becoming an integrated issues, corporate advisory and brand reputation partner for clients."
Grayling employs around 400 people in Europe. Revenue figures for the continent are not available, although the agency globally saw like-for-like revenue fall 3.2 per cent to £17.1m in the first half of 2019. Losses narrowed from £0.3m to £0.1m.
Announcing the half-year results in July, Huntsworth said the UK "continued to be the standout performer" at Grayling, with 10.9 per cent like-for-like revenue growth "on the back of further good client wins".