Mo. Rev. Stat. § 429.300
The equitable action above provided for shall be brought in the proper court of record regardless of the amount claimed by the plaintiff or plaintiffs in such action, and all other suits that may have been brought on any mechanic's lien claim or demand shall be stayed and no further prosecuted, and the parties in any such other suit shall be made parties to such equitable action as in the foregoing sections provided, and any costs rightfully accrued in behalf of any lien claimant in any such other action shall be and become a part of the lien claim of such party. After the institution of such equitable action no separate suit shall be brought upon any mechanic's lien or claim against said property, or any of it, but the rights of all persons shall be adjusted, adjudicated and enforced in such equitable suit.
§ 429.300, RSMo