diff --git a/protocol-designer/src/pages/Designer/ProtocolSteps/Timeline/SubstepsToolbox.tsx b/protocol-designer/src/pages/Designer/ProtocolSteps/Timeline/SubstepsToolbox.tsx
index e2460741ebf..eb0a0ba835b 100644
--- a/protocol-designer/src/pages/Designer/ProtocolSteps/Timeline/SubstepsToolbox.tsx
+++ b/protocol-designer/src/pages/Designer/ProtocolSteps/Timeline/SubstepsToolbox.tsx
@@ -58,6 +58,7 @@ export function SubstepsToolbox(
       substeps.commandCreatorFnName === 'mix')) ||
     substeps.substepType === THERMOCYCLER_PROFILE ? (
     <Toolbox
+      height="calc(100vh - 6rem)"
       width={FLEX_MAX_CONTENT}
       closeButton={<Icon size="2rem" name="close" />}
       onCloseClick={handleClose}