Collaborative spatial decision support tools can contribute with setups for including stakeholders into marine spatial planning (MSP) processes with the purpose of increasing trust in planning outcomes, facilitate knowledge co-creation and shared planning goals, and provide transparent, scientific, inclusive, and technical foundations for planning. A new collaborative spatial decision support setup based on the combination of functionalities from two spatial decision support tools called SEANERGY and Baltic Explorer was designed for and tested in a workshop in 2020 targeted local authorities, NGOs, and citizens in Denmark with an interest in MSP. While the setup needs further testing among a wider span of stakeholders to support a pluralistic approach, the findings illustrate promising potentials from ranking conflicts and synergies in collaborative settings to make marine activity interests spatially visible in MSP and gain an overview of opportunities for sea use multi-functionality in context-based, interactive, goal-oriented stakeholder processes. The use of a visual platform such as Baltic Explorer to systematically explore locations of marine uses was positively evaluated to facilitate the workshop conflict-synergy discussions. Challenges relate to how to deal with disagreements on conflict-synergy scores and the subjectivity of opinions, but the demonstrated flexible, quick, transparent way to test the sensitivity of spatial patterns to differences in input conflict-synergy scores is found to provide a promising setup for including stakeholder opinions through collaborative settings, a setup adjustable to supplementary large-scale, individual, more representative surveys as well.